1. Field of the Invention
The present invention relates to a system and an information processing method and apparatus that carry out channel switching in response to communication conditions.
2. Description of the Related Art
Heretofore various techniques have been proposed for making efficient use of the frequency resources of wireless LAN. US2002/188723 (Japanese Patent Application Laid-Open (Tokuhyo) No. 2004-520766) discloses a mechanism by which a wireless access point is moved to a new channel, more specifically, concerning selecting a channel having a “smallest RSSI (received signal strength indication)” and/or a “smallest CCA (clear channel assessment).” Furthermore, IEEE 802.11h-2003 shows a procedure in which channel quality measurements and switching are carried out with an IEEE 802.11 management frame. Further still, US2002/176437 (Japanese Patent Application Laid-Open No. 2003-32268) discloses a technique in which an optimal channel is selected using a regular channel quality parameter (regCSIQ) and channel exchanges (swaps) are performed among a plurality of access points.
These conventional techniques aim to improve communication quality by switching to another channel when the number of communications terminals connected to a single wireless access point increases and causes competition, which worsens communication quality.
However, in these conventional wireless communications systems, the determination of whether or not it is necessary to switch to a new channel is based on only channel quality resulting from having carried out communications. That is to say, the communication channel is moved after the communication quality has actually worsened. For this reason, in a case where, for example, multicast communications of stream data are received and recorded in real time without buffering, a problem arises of stream data being lost. That is, even for unrecoverable communications such as this, conventional systems carry out a process for improving quality after communications (recording) have begun and quality has worsened.
Along with the spread of wireless products in recent years, channels of multiple frequencies have begun to be used in a single system or living space. In these systems, channels are assigned so that there is no interference in the radio waves to be used. However, the number of channels assignable without interference in IEEE 11b/g and IEEE 11a is from 3 to 8 channels and in environments such as collective housing where many more users than that are concentrated, a multitude of wireless access points become arranged within a communications radius such that the arrangement inevitably results in channel interference.
For this reason, conventionally measures are taken in which reductions are made to the transmit power of the access points and the terminals causing interference to narrow the communications radius of the access points. However, such algorithms, which imply “if interference occurs, lower each other's transmit power,” involve reducing one's own transmit power and such reductions in transmit power may also potentially cause problems in wireless communications. For example, when a distance between the access point in a residence of a certain user A and the access point in a neighboring residence is shorter than the distance between the access point and the terminal in the user A's system, reducing the transmit power may disable communications. However, generally access points have wired connections to a wired LAN, and therefore the installation location of the access point is limited and not easy to move. And of course it is not realistic to have the neighboring residence move its access point. Eventually the transmit power is reduced at the position where the access point is currently installed and it becomes impossible to establish a sufficient radio environment between the access point and the terminal.
On the other hand, when access points of a same channel are present within the communications radius, there is a method of maintaining communications by sharing bandwidth of for example 54 Mbps within the channel without reducing the transmit power. However, this eventuates in communication quality deterioration when the total used bandwidth of wireless stations connected to the access points on that channel exceeds 54 Mbps.